It’s time to pump you up, baby! Don’t you just love it? Don’t you just love the gym? You may not like stopping by the gym on your way home from work, but your brain certainly does. Just think about the boost in positive self-perception that comes from deliberate suffering, much the way historical fanatics might have worn hair shirts or walked down the road whipping themselves repeatedly with knotted ropes (a practice that informs many exercises in the modern discipline of CrossFit). Okay, the silly austerity of self-imposed masochism isn’t the only reason to work out. It’s also good for the physical structure of your brain.
For decades we’ve seen the brain-training effects of a physically enriching environment on lab animals: mice with the opportunity to exercise learn faster than mice in the proverbial six-by-eight cell with a cup of water and a crust of dry bread. And it’s not just mice. In fact, a huge combination of studies that looked at the relationship between physical exercise and brain skills in kids ages four to eighteen found improved scores on perceptual skills, intelligence quotient, achievement, verbal tests, mathematics tests, memory, developmental level, and academic readiness for kids who exercised. At the other end of the age spectrum, exercise protects older adults from many forms of cognitive decline associated with aging, potentially even pushing back the onset of Alzheimer’s disease.
One reason is the chemicals released in your brain during exercise, like brain-derived neurotrophic factor or BDNF. Don’t look for it in the list of ingredients on that jar of macho muscle supplement. Instead, BDNF is a protein made by the BDNF gene that helps the brain change itself to meet the needs of the environment. The brain’s ability to adapt is called neuroplasticity, and it depends in large part on BDNF. Researchers see BDNF levels go up in exercising humans and mice, and afterward they can see improvements compared to sedentary humans and mice in things like running mazes (that’s for the mice, not the humans). When researchers blocked the activity of BDNF in mouse brains, they showed no improvement in maze running after exercise—it was the chemical induced by exercise that increased the rodents’ ability to learn about their surroundings.
These chemicals released during exercise also affect mood. For example, you’ll read about dopamine, serotonin, and norepinephrine in this book’s entry about love. Well, guess what? These same chemicals are secreted during exercise. Dopamine is physically pleasurable, serotonin creates the feeling of awake energy, and norepinephrine increases alertness and arousal. Combined, these chemicals perk you up. There’s a lot to be said for taking a nap when you’re tired, but there’s also a lot to be said for its opposite—when you’re feeling physically or mentally tired, cardiovascular exercise can transform the chemical landscape of your brain into one of focused energy.
Exercise also helps oxygen and nutrients move through your body, and part of your body is your brain. The Greeks said mens sana in corpore sano, meaning “a sound mind in a sound body,” and it’s increasingly clear that the link between the two is the cardiovascular system. When you train your heart and lungs, they are better able to deliver oxygen and nutrients to your brain—studies have shown up to a 40 percent difference in gray matter volume between people who exercise and those who don’t in areas including the cingulate cortex, the prefrontal cortex, sections of the dorsal anterior cingulate cortex, the supplementary motor area, and the middle frontal gyrus. You won’t be tested on the names of these structures—the point is that exercise creates cardiovascular health, and cardiovascular health literally creates larger brains. This is true to the point that when people are prescribed exercise, researchers can see gains in brain volumes. For example, a 2011 study published in the Proceedings of the National Academy of Sciences with the optimistic title “Exercise Training Increases Size of Hippocampus and Improves Memory” shows just that: in a sample of older adults, the hippocampi of people who exercised grew by about 2 percent over the course of the year, while the hippocampi of people who didn’t exercise shrank by about 1 percent. The memory outcome makes sense: your hippocampus helps you create new memories.
Despite the demands of most indoor jobs in the Internet age, humans are not meant to sit and think. (Take a look at carpal tunnel statistics and you’ll see we’re not meant to sit and type, either.) In fact, the traditional idea of sitting and thinking may be just about the worst way to bring brainpower to bear on tricky problems. If you want your brain to function at its best, give it what it wants: exercise.
You Gotta Love It
A host of studies shows why we don’t exercise: we think it’s going to suck. And the long-term reward of better health can’t touch the short-term dread that exercise will be difficult and awful. If you want long-term health for your body and your brain, it’s time to find some kind of exercise that you don’t dread. Be it Sweatin’ to the Oldies or walking the dog, unless your brain works differently than the brains of most people, the only way you’ll stick with your exercise routine is if you like it.